Information hiding technology can hide one piece of information into another piece of carrier information without a user's awareness, and such a technology plays a very important role in many aspects of an information security system. A text digital watermark technology, as a branch of the information hiding technology, uses a text as a carrier and embeds digital watermark information by finding a redundancy space of text information.
Usually, the digital watermark information is embedded into the text based on document format characteristics in the prior art. Such a method uses typesetting characteristics of a text format itself and visual redundancy characteristics of human beings, and embeds a watermark through fine-tuning of the text format. For example, one-bit watermark information may be encoded and embedded into a row by slightly changing the line spacing. It can therefore be seen that, when the length of the text is limited, merely a small amount of information may be embedded into the text if an existing digital watermark embedding method is used.